In previous works entitled “Thiation of Carbon Nanotubes and Composite Formation” (U.S. Pat. No. 7,713,508 B2) and “Antennas Based on a Conductive Polymer Composite and Methods for Production Thereof” (U.S. Pat. No. 8,248,305 B2), the formation of a highly conductive composite through tight networks of interwoven carbon nanotube bundles was demonstrated. Binding nanotubes into large, but tight bundles, dramatically alters the morphology and electronic transport dynamics of the composite. This enables the composite to carry higher levels of charge in the macroscale leading to conductivities as high as 1600 S/cm. When controlled and used appropriately, the interesting properties of these composites reveal their potential for practical device applications, such as improving the properties of an electromagnetic (EM) antenna/amplifier transducer. An electronic transducer was fabricated where the composite film can receive broadband radio waves up to GHz frequencies and convert them to measurable current. The benefit of this coating is that it can be used as an EM amplifier in the presence of other metals.
In additional to carbon nanotubes, graphene has attracted much attention in the past few years. Graphene possesses unique electronic properties, such as the quantum hall effect in condensed-matter materials and excellent mobility of charge carriers due to its unique π-conjugated carbon monolayer 2D system. Based on these qualities, many researchers have focus on the development of graphene-based electronic devices. However, understanding of EM attenuation/amplification properties of graphenes or graphene oxides is still limited. By using liquid-phase exfoliation of graphite in common organic solvent such as N-methyl-2-pyrrolidone (NMP), graphene/graphene oxide dispersion can be produced with high-yield. Because of the strong π-π interactions, graphenes/graphene oxides are expected to process strong EM attenuation/amplification properties.
An important topic in nanocomposite material science is the design of multi-functional materials, which simultaneously allow one to satisfy several characteristics which are required for specific applications. For example, EM attenuation/amplification properties of graphitic nanocomposites are very useful for designing novel antenna or shielding/cloaking devices without using any metal components. More specifically, EM attenuation property of graphitic nanocomposites can reduce the intensity of incoming waves with selective wavelengths, which can be used as shielding (to block the EM wave passing through) or cloaking (to reduce the EW wave reflected back) devices. On the other hand, when applying graphitic nanocomposites on antenna devices, the EM amplification property allows selective wavelengths to be amplified and thus increase the power of selective signals. In addition, the increasing strength of graphitic nanocomposites is very valuable for increasing durability of many common plastic components. Although the study of controlled propagation of EM waves using nanomaterials is currently one of the most active fields of research, the scope of the research is still focused on the basic understanding of the mechanisms usually in a liquid dispersion. In order to apply to practical/commercial use, these nanomaterials need to be embedded into solid state matrices (e.g. bulks or thin films) while still maintain their unique EM properties. This becomes a significant challenge because there are many fundamental differences between liquid dispersions and solid state matrices. One example to illustrate this challenge is the design of organic systems such as molecules and polymers with π-conjugated electron system (e.g. carbon nanotubes and graphenes). Photophysical properties deriving from the transitions between different electronic states are extremely dependent on the environment of these nanomaterials. Decreasing of these responses due to decreasing of the quantum yield is observed as a consequence of large aggregation in the solid matrix. However, it also provides an opportunity if one can design a functional solid matrix having the interactions with the graphitic nanomaterials to perturb its molecular orbitals to increase the corresponding transitions, which is otherwise weak in a simple organic solution. The key is an accurate choice of the solid state matrix and preparation of the nanocomposites which not only preserve the dispersed state of the graphitic nanomaterials but also strengthen the desired EM properties through the synergic interplay between the solid state matrix (host) and the graphitic nanomaterials (guest).
To use a variety of graphitic nanomaterials such as carbon nanotube, graphene or carbon black as fillers for their electronic properties for antenna or EM shielding applications, different approaches are needed when forming each composite. Many researchers have tried to incorporate carbon nanotubes or graphenes in bulk polymers such as poly(methyl methacrylate) or polystyrene, but only with a very low concentration (e.g. less than 1.0 w/v %) before these nanomaterials start to aggregate due to the incompatibility between the polymer (host) and the graphitic material (guest). In previous works entitled “Waterproof Coating with Nanoscopic/Microscopic Features and Methods of Making Same” (U.S. patent application Ser. No. 14/277,325 filed May 14, 2014 claiming priority to U.S. Provisional Patent Application 61/823,127 filed May 14, 2013, which is hereby incorporated by reference in its entirety), it was demonstrated how to apply a silane based sol-gel system to produce waterproof coating on a variety of substrates.
Overcoming the abovenoted aggregation issues would allow higher concentrations graphitic nanocomposite materials to be produced. Systems and methods discussed herein utilized graphitic nanomaterials that are functionalized with a functional group with a moiety similar to a desired solid state matrix. The functionalized graphitic nanomaterials may be mixed with sol-gel chemicals and cured to form a homogeneous graphitic nanocomposite material.